Hydraulically operated presses



July 26, 1960 Filed NOV. 1, 1957 M. SCHMID 2,946,303

HYDRAULICALLY OPERATED PRESSES 4 Sheets-Sheet 1 WAfH/AS SCH/VA July 26,1960 M. SCHMID 2,946,303

HYDRAULICALLY OPERATED PRESSES Filed Nov. 1, 1957 4 Sheets-Sheet 2FREQ/PE /N FREQ CYLINDER a a b c c MOVEMENT 0F mass cyan/05R MATH/A5SCH/V/D July 26, 1960 M. SCHMID HYDRAULICALLY OPERATED PRESSES 4Sheets-Sheet 3 Filed Nov. 1, 1957 Inveman MATH/A5 SCH/7Z2 v 1960 M.SCHMID 2,946,303

R HYDRAUL-JICALLY OPERATED PRESSES Filed Nov. 1. 1957 4 Sheets-Sheet 4Inventor? MATH/A5 5 (l/MID Fania HYDRAULICALLYUPERATED PRESSES MathiasSchmid, Krefeld, Germany, assignor to G. Siempelkamp and Company,Krefeld, Germany Filed Nov. 1, 1957, Ser. No. 694,042

Claims priority, application Germany Feb. 1, 1957 18 Claims. (Cl. 113-45) Hydraulically operated presses, particularly extrusion presses ordrop-forge presses are, in most cases up to now, driven directly byair-cushioned high-pressure water accumulators. With such knownarrangements, it is difiicult to accomplish the forming and relievingoperation of a press within short time intervals as is often necessaryor at least desirable in order to attain the proper speed for theforming process which speed depends, on the type of material to beformed or on other reasons. Particularly, the forming of hot titaniumsheets becomes difiicult if done in presses employing a rubber pad orcushion as a counter die and in which the time for forming and relievingis of relatively long duration inasmuch as the rubber pad is unable towithstand the application of high temperatures over a relatively longperiod of time as it will heat up to a point where the rubber is damagedor destroyed.

This problem for forming hot workpieces becomes particularly acute whentitanium is used in place of conventional aluminum rnctalstwhich may beformed in a cold condition, as, for instance, in the manufacture of theskin of aircrafts or rockets which travel at supersonic speeds. Theproduction of forged titanium parts in a conventional manner with astationary die and a rubber pad or other resilient material as a counterdie, leads to difiiculties inasmuch as titanium, contrary to aluminumalloys, must be formed at extremely high temperatures. Since a counterdie made of rubber rapidly loses its strength when heated, titaniumcannot be forged successfully with conventional presses employing arubber pad as a counter die.

in order to overcome these difficulties, it was suggested to employ drophammers for forging titanium workpieces, particularly sheets, so as toshorten the time of contact between the forming tool and the hot wor.piece and thereby avoid undue heating of the rubber. However, theefiiciency of such drop hammers is very poor due to the fact that thehammer, in forming titanium sheets, must consist of a rubber block.

it is, therefore, an object of the present invention to accelerate theforming and relieving operation of hydraulically operated presseswithout the necessity of unduly increasing the high-pressure accumulatoror of intolerably increasing the pressure level therein.

Therefore, the present invention relates to hydraulically operatedpresses, particularly extrusion presses or drop-forge presses employingrubber pads which are operated, for instance, by means of an aircushioned highpressure accumulator. The invention resides therein that ahigh-pressure transformer is arranged between the high-pressureaccumulator and the press by which the actual forming process isaccomplished after the press has been initially closed. This pressuretransformer is operatively adjustable in various ways so that its:operation is advantageously suitable for the forming process. It-isadvantageous to also arrange a low-pressure trans.-v former between thehigh-pressure accumulator and the press for efiecting the initialclosing operation thereof.

2,946,303 Patented July 26, 1960 In order to assure-continuous operationof the hydraulic press without special attention, the functional controlthereof, according to the present invention is such, that after thepress has initially closed and the actual forming process is about tocommence, the highpressure transformer is automatically brought intooperation by making use, for instance, of the pressure rise which occursin the press cylinder as the workpiece is brought into contact with therubber pad or counter die at the end of the initial press closingoperation. For this purpose, appropriate control valves may be combinedwith the pressure transmitters, as required.

The advantages which are attained with the arrangement according to thepresent invention, above all, reside therein that it is possible withpresses of this type to perform the actual forming of the workpiece inan extremely short time, even with the largest size presses. It is, forinstance, possible to close the press, up to a point where the dietouches the rubber pad, in a few seconds and to perform the actualforming process in one or two seconds and to completely retract theforming tool in a few additional seconds.

A further essential advantage of the present arrangement resides thereinthat, contrary to hydraulic presses which are directly driven byhigh-pressure accumulators, considerable energy is saved, as will beexplained in more detail later on.

Finally, in an arrangement according to the present invention, theworking pressure in the press may be increased markedly whereby thepower actuating parts may be made smaller and, as a result thereof, thespace required becomes less than for arrangements wherein the press isactuated directly from an accumulator.

As an added feature of the present'invention, the lowpressuretransformer includes a small high-pressure piston combined with alowpressure piston of the size corresponding to the weight of the partsthat must be moved .in initially closing the press. It is especiallyadvantageous, as mentioned above, to control the pressure in thehigh-pressure transformer during the forming process in such a way thatit coincides with the pressure characteristic actually required for theforming operation. A further saving on energy is thereby possible,inasmuch as the pressure rise thus coincides with that actually desiredin the press during the forming operation whereby the expended energy islimited to the absolute required amount.

The high-pressure transformer itself consists, in itssimplest form, ofdriving and driven pistons whereby, through transmission of forces fromthe driving piston which is supplied by the high-pressure accumulator tothe driven piston, the pressure transformation and control thereof isaccomplished. Preferably the movement of the driving pistons isperpendicular to that of thedriven pistons and the pistons are directlyinterconnected with each other by connecting rods so that, in thesimplest manner, the rise in pressure at the driven pistons coincideswith the pressure characteristic desired in the press.

In order to require only a single high-pressure transformer in thepresent arrangement, regardless of the height or depth of the die, thepressure rise in the highpressure transformer is; limited by a'pressure-limit valve. This pressure-limit valve may beconnected to thedriving pistons, respectively, to their cylinders. Furthermore, it ispreferable that the high-pressure transformer is constructed in such away that it operates at the same time as acontrol of the press pressureduring the unloading of thepress as, for instance, in such a way thatthe two driving pistons of the high-pressure transformer are arrangedcoaxially intwo. cylinders and that these two pistons are connected witheach other by a rigid piston rod while the connecting rods of the drivenpistons, which are attached thereto, move in a direction substantiallyperpendicular to the movement of the driving pistons.

With such an. arrangement, a variable force ratio between drivingpistons and driven pistons is attained in a mostjsimple mannerand at thesametime a'variablepressure transformer that works as follows:

. The driven pistons, at the beginning of their movement, produce only asmall hydraulic pressure while at the dead center position of theconnecting rods they theoretically produce an infinitely large hydraulicpressure whereby thedelivery of these driven'pistons in relation to thetravel of the driving pistons is in the inverse ratio to the pressurethey produce. It can easily be seen that the hydraulic pressure in sucha pressure transformer increases along a similar characteristic asisdesirable in drop-forges and particularly extrusion presses withrubber pads. A further advantage in the operation of the presenthydraulic press resides thereinthat it is possible to have 4 porates aconventional solid die 2 and a rubber cushion 3 that acts as a counterdie. The pressing or forming operation of the workpiece S isaccomplished with a conventional press piston or ram 4 and the generalstructure of the press itself, being also of conventional design, doesnot need to be described in detail.

For the hydraulic operation of the press, a conventional accumulator 5with a working liquid, such as water, is provided. The water in theaccumulator 5 is kept under pressure in a conventional manner bycompressed air. The Water is supplied to this accumulator 5 by a pumpthrough the pump discharge line 21. This line 21 includes a check valve22, an automatic shut-01f valve 23,

leads to an operating control valve assembly -29 including thepresspiston or ram as well as the driven piston of,

the high-pressure transformer operate with oil, whereas, the drivingpistons of the pressure transformer and the high-pressure accumulatorcan be operated with water.

Accordingly, an object of the present invention is to provide ahydraulically operated press in which the time two control valves 2% and2%. From the valve assembly 29, a line 30 leads to the cylinder space 32of a low pressure transformer 31 which includes a differential piston 33comprising a smaller high pressure piston 33a and a larger low pressurepiston 33b.

for the forming and relieving process can be reduced to any desiredvalue regardless of the size of the press.

It is another object of the present invention to provide a hydraulicallyoperated press in which the high-pressure accumulator is of relativelysmall size and the working pressure therein of relatively smallmagnitude.

Another object of the present invention resides in the relativelysmallsize of the force transmitting parts as well as the high etficiency ofthe working cycle.

-A further object of the present invention resides therein that the rateof pressure rise of the operating fluid in the press cylinder increasesduring the forming process and that the pressure reaches a maximum asthe forming process is completed. 7

Still another object of the present invention resides there nthat theforming and relieving process may be accomplished extremely fast by theinventive action of thehigh-pressure transformer, becausea reversal ofthe fluid flow to the driving piston of the transformer is not requiredduring the two above-mentioned processes. I These and further objectsand advantages of the present inventionwill become more obvious from thefollowing description of a hydraulically operated press when taken mlconnectionv with the accompanying drawing which shows, for the purposeof illustration only, several embodiments in accordance with the presentinvention, and wherein: r Figure l is a schematic arrangement of thehydraulically operated press in accordance with the present invention. 7

Figure 2 is a diagram showing the pressure course in the high pressuretransformer and press cylinder during one complete press cycle;

- Figure 3 is a schematic arrangement of the hydraulically operatedpress according to the present invention showing the essential elementsfor automatic operation thereof;

. Figure 4 is a cross-sectional view through the lowpres suretransformer of a modified construction;

, Figure 5, is a cross-sectional view through the highpressuretransformer; and

Figure 6 is a cross-sectional view through a modified various views todesignate like parts,the extrusion or drop-forge press which, asillustrated in Figure 1, incor- A second line 34 branches off the highpressure line 21 leading to operating control valve assemblies 35 and36, each of which includes two valves 35a, 35b and 36a, 36b,respectively. Lines 37 and 38 lead from the valve assemblies 35 and 36to cylinder spaces 39 and 4th of a high pressure transformer 41. Withinthe cylinder'spaces 39 and 4t), driving actuator pistons 39a and 4011are slidably arranged and are rigidly connected with each other.

Lines 42 and 43 branch oif from lines 37 and 33 and 7 lead to a checkvalve assembly 44 consisting of two check valves 44a and 44b. The checkvalve assembly 44 in '7 turn is connected to a cylinder space 45a in thepressure limit valve 46 through line 45. The pressure limit valve 46comprises a cylinder space 49 and a difierential piston valve 47slidably arranged in the cylinder spaces 45a and 49 and is spring loadedby a spring 43. The control valves 2%, 35b and 36a are connected throughline 51 to the water reservoir 27.

The cylinder space 52 above the dilierential piston 33b which contains aworking fluid, preferably oil, is in communication with the presscylinder 40 through line 53 in which a check valve 54 is arranged. Aline 56 branches ofi the line 53 behind the check valve 54 and leads toa spring loaded pressure limit valve 57 and from there continues to thecylinder space 49 of the pressure limit valve 46. A line 55 leads fromthe cylinder space 49 to the oil reservoir 64, while a line 55 leadsfrom the discharge side of the pressure limit valve 57 to the reservoir64.

A second line 58 is connected to line 53 behind the check valve 54 andleads to an operating control valve 59 and from there connects to theintake of a check valve 60. The discharge side of the valve 60 isconnected to line 53 ahead of the check valve 54 through line 61 whilethe intake side thereof is connected to the oil reservoir 64 throughline 65.

The high pressure transformer 41 further comprises two driven pistons 66and 67, the center line of which is preferably disposed perpendicularlyto the center line of the driving pistons 39a and 40a and which areslidably arranged in cylinders 66a and 67a. The driven pistons 66 and 67are operatively connected to the driving piston assembly 39a, 40a, byconnecting rods 68a and 68b at joint a. From the cylinder spaces '66::and 67a of the high pressure transmitter 41, lines 69 lead to line 56.

Operation I Assuming the press piston 4, die 2 and the workpiece 8 arein the position as shown in Figure l, the press is initially closed,i.e., the press piston is moved up until the workpiece 8 touches therubber cushion 3. This initial movement of press piston or ram 4 is,accomplished by opening valves 23, 2:4 and 29a, whereby water underpressure of about 300 kg./cn 1. from the high pressure accumulator isadmitted to the cylinder space 31 through lines 21, 28 and 30. Thedifferential piston 33 is thereby raised whereby the oil in the cylinderspace 52 is forced by the piston 33b into the press cylinder 4a wherebythe press piston or ram 4 is also raised in turn thereby exerting aslight pressure on the workpiece as it comes into contact with therubber cushion 3. Due to the fact that the diameter of the piston 33b ofthe differential piston 33 is considerably larger than the piston 33a,thev specific pressure exerted on the ram 4 is con-. siderablysmallerthan that in the high pressure accumulator 5; that. is, thepressure in the cylinder 4a is reduced in the ratios of the areas ofpistons 33b to 33a. Actually, the piston in the press cylinder 4a mustonly be of a magnitude suificient to raise the moving weights of thepress 1 during initial closing of the press.

The speed of the upward movement of the diflerential piston 33 whichalso determines the speed, of the upward movement of the ram 4 duringthe initial closing operation of the press may be adjusted to anydesired value by adjusting the flow area through the check valveassembly 54, as, for instance, by limiting the lift of the check valveor by other means.

When initial closing of the press is completed, valves 35a and 36b areopened and pressure fluid from the accumulator 5 is applied to thecylinder space 3 9 of the high pressure transformer 41. As a result, thepiston assembly 39a, 46a is moved to the left. At the, same time,working fluid, that is, water remaining in the cylinder space 40, isdischarged through the open valve 36b and 1ine51-to the water reservoir27.

As a result of the movement to the left of the driving piston assembly39a, 4% from a position a to a position b, the driven pistons 66 and 67are moved outwardly by means of the connecting rods 68a and 6%, therebydisplacing the oil in the cylinder spaces 66a and 67a through lines 69,56 into the pressed cylinder 4a. As a result thereof, the ram 4 togetherwith the die 2 are moved upwardly whereby the actual forming operationof the workpiece 8 is performed.

Asthe driving piston assembly 39a, 40a continues its movement from theposition b to the position 0, the driven pistons 66 and 67 reverse thedirection of their outward movement and are now moved inwardly to theirinner dead center. This inward movement of pistons 66 and 67 effectsdrawing of working fluid from the press cylinder 4a through lines 56 and'69 into the cylinder spaces 66:; and 67a and as a consequence of thiswithdrawal of oil from the press cylinder 4a, the pressure therein isrelieved and the press piston 4 begins to move downwardly and effectsopening of the die 2 to a point where it formerly began the actualforming operation.

In order to further open the press to remove the finished workpiece 8therefrom, valve 29a is closed, and valves 29b and 59 are opened. Theoperation of valve 29b, on the one hand, permits the water in thecylinder space 32 to escape through line 51 into the water reservoir 27and opening of the valve 53, on the other hand, establishescommunication between the cylinder spaces 4a and 52 through line 58,control valve 59, check valve 60 and line 61. As a result, thedifferential piston 33 in thelow pressure transformer 31 movesdownwardly by its own weight or by spring means drawing oil out of thepress cylinder 4a whereby the press piston 4 together with thedie 2 arealso allowed to move downwardly to thereby open the press to its initialstarting position.

The speed of the downward movement of the differential piston 33, whichalso determines the speed of the downward movement of the ram 4 duringthe opening operation of'the press may be adjusted to any desired degreeby corresponding dimensioning of the flow passages through the valves 59and 60 as, for instance, by limiting the effective lift of these valvesor other means.

A 2. thered from the description of the operat tion, it is. apparentthat the, movement of the press ram 4 and die 2 during the actualforming operation of the workpiece, 8 is produced by the movement of thedriving piston assembly 39a, 40a from a position a to the centerposition b. and the corresponding outward movement of the driven pistons66 and. 67. The movement of the driving piston assembly 39a, 40a fromthe center position b to the position 0 produces the relieving movementof the press piston 4. The fluid pressure characteristic in the presscylinder during this movement from a to c is represented in the diagramof Figure 2. The positionsv a, b, e indicated thereon represent thecorresponding positions of the press ram 4 during the forming and therelieving operation. The distance a'.a represents the initial closingmovement of the press piston, whilev the distance c-.c'representsopening of the press to its initial starting position. Thepressure in the press cylinder 4a during the initial closing of thepress rises very slightly, as shown in the diagram, While during theforming operation the pressure rises rather rapidly attainingtheoretical infinity at position b. It is also apparent from the diagramof Figure 2 that with this mode of power transmission from driving todriven pistons a variable pressure transmission is created wherewith thedriven pistons 66 and 67 produce only a small pressure at the beginningof their outward movement while they produce a theoretical infinitehydraulic pressure as they reach their outermost position correspondingto the position b and the working fluid delivered by these; drivenpistons is in the inverse ratio to the distance travelled by the drivingpiston assembly 359a, 40a. Accordingly, it is apparent that thehydraulic pressure produced by the pressure transformer 41 increasesduring the forming operation in amanner which is desired in theoperation of a drop-forge press.

Inasmuch as an. infinite pressure can be produced with the high pressuretransformer 41, its absolute magnitude is limited by apredeterminedsetting of the pressure limiting valve 57. Dueto the tact that theforming stroke of the press must be variable to accommodate variousshapes of workpieces, it could happen, with shallow dies for instance,that the maximum pressure is obtained at a position of the driving:piston assembly 39a, 49a between a and b. In order to be sure that thedriving piston assembly 39a, 40a in every case moves from a to 0 underthe pressure. available from the accumulator or pump, the spring 48- in,the pressure limit valve 46 is so adjusted that the differential pistonvalve 47 is moved upwardly if the pressurein line 45 and cylinder space45a reaches a magnitude equalto the pressure. of the accumulator minus10 percent. If the pressure in the cylinder space 45a and line 45reaches such a magnitude, the differential piston valve 47; movesupwardly whereby communication between the press cylinder 4a and. theoil reservoir 64 is established through lines. 5 6 and 55. Under suchcondi tions, the pressure in. the press cylinder 4a, produced by thehigh pressure transformer 41 remains constant over the remaining part ofthe forming stroke of the press. The, 10 percent pressure diiierentialis needed to overcome the flow resistance from the high pressureaccumulator 5 to the driving pistons 39a and 40a of the high pressuretransformer 41. The pressure limit valve 46 provides an assurance thatthe driving piston assembly 39a, 40a does not become stuck at a pointbetween a, and b due to excessive resistance to movement produced, inthe cylinders 66a and 67a of the driven pistons 66 and 67.

It should be noted that with such any arrangement the direction of thedriving fluid to the driving pistons. 39 a and '40:; during the formingand relieving stroke of the press does. not have to be reversed as isthe case in, con; ventional hydraulic presses in which a reversal of thedriving fluid occurs subsequent torthe completionof the formingoperation. i

Inasmuch as there is no reversal of direction ofa driving fluid from theaccumulator 5 necessary during the 7 forming and relieving operation,the present arrangement presents a way for closing and relieving pressesin the shortest possible time. q J

To start a newpres-s cycle'the operation as outlined above remains thesame except that after the initial closing of the press, valves 36a and35b are opened which produces a movement of the driving piston assembly39a, 40a from a position c back to the original position a.

It is understood that the various operating control valves 23, 29a, 29b,35a, 35b, 36a, 36b and 59 ,could be operated either manually,hydraulically, pneumatically, electrically, mechanically or by any othermeans and further that liquids other than water and oil could be used asworking fluids. I

The arrangement shown in Figure 3 difiers from that shown in Figure 1only to the extent that the various steps in the operation of thehydraulic press, according to the present invention, are performedautomatically. To accomplish automatic operation, the pump 20, thesuction side of which is connected to the water reservoir 27 throughline 26, discharges into line 101 which is in com munication with thehigh pressure accumulator and an operating control valve 102. A line 103connects valve 102 with an automatic reverse valve 104. This automaticreverse valve consists of -a piston 105 slidably arranged in thecylinder 106 and urged to one side of the cylinder 106 by a spring 107.A piston valve 108, comprising two collars 109 and 110, is slidablyarranged in a cylinder 111 which is separate from the cylinder 106. Thepiston 105 is connected with the piston valve 108 by a connecting rod112. V

-A line 113 leads from cylinder 1111 to the cylinder space 114 of thelow-pressure transformer 115. The construction and functioning of thelow-pressure transformer 115 is similar to that described in connectionwith Figure 1 except that a spring 116 is provided which tends to forcethe differential piston assembly 11 7 downwardly at all times. A line120 branches off line 113 and is con-. nected to the cylinder 106 of theautomatic reverse valve 104 and a second line 118 connects line 113 withan operating control valve 119. A return line 121 connects valve 119with the water reservoir 27.

A second line 126 leads from cylinder 111 of the automatic reverse valve104 to a four-way valve 127, and lines 128 and 129 connect the four-wayvalve 127 with the cylinder spaces 139 and 140, respectively, of thehigh pressure transformer 141. The four-way valve 127 is also connectedwith line 121 through line 130. Line 126 and consequently cylinder 111are further in communication with cylinder 132 of a pressure limit valve133, wherein a piston 134 is slidably arranged in the cylinder 132 andis urged to one side thereof by a spring 136. A valve piston 135 isslidably arranged in a cylinder 137 which is separate from cylinder 132.The piston valve '135 divides the cylinder 137 into two cylinder spaces122 and 123. A piston rod 138 connects piston 134 with piston valve 135.

The cylinder space 152 of the low-pressuretransformer is incommunication with the press cylinder 4a through line 53 including acheck valve 54 similar to the arrangement shown in Figure 1. A by-passline 124 around the check valve 54 includes an operating control valvev14 2. The control valves 102, 119 and 142 are operatively connectedtogether by a connecting rod 143 so that they may be operatedsimultaneously.

-A line 143 in communication with the cylinder spaces 166a and 167a ofthe high-pressure transformer 141 is connected to line 53 between thecheck valve 54 and press-cylinder space 4a. A line 144, which includes acheck valve 145 connects line 143 with the oilresenvoir 64. a 1

Cylinder space 123 is in direct communication with the oil reservoir 64while line 1143 is also" connected to cylinder137 of the pressure limit:valve 133.

Automatic operation The automatic operation of the present hydraulicallyoperated press is explained on hand of the schematic flow diagram ofFigure 3, as follows:

The pump 20 draws water from the reservoir 27 and matic reverse valve104 through line 103 and from there into cylinder space 114 of thelow-pressure transformer 115 through line 113, moving the piston 133aupwardly. The piston =133b which is rigidly connected to the piston 133athrough a piston rod 116 compresses the oil in the cylinder 152 to apressure equal to the accumulator pressure reduced in the ratio of thepiston area 1331) to 133a. As a result, the oil in the cylinder space152 is pushed through line 53 and the check valve 54 into the presscylinder 4a of the press 1 and moves the'press plunger or ram 4upwardly. The die 2, Figure 1, with the working piece 8 resting thereon,is :also moved upwardly until the workpiece 8 contacts the rubber pad orcounter die 3. When this occurs,the pressure in the cylinder chambers4a, 152 and 114 begins to rise.

If the pressure in the cylinder space1 14 and 106, which acts on thepiston of the automatic reverse valve 104, rises sufficiently toovercome the force of the spring 107, the control plungers 109 and aremoved to the right and the water from the high-pressure accumulator nowflows through line 126 to the four-way valve 127 and to the highpressure transformer tl. v

In the position as shown in Figure 3, the four-way valve 127 allows theflow of water into the cylinder space 139 and forces the plunger 139a tothe left whereby the water remaining in the cylinder chamber 140-isforced through line 129, the four-way valve 127, line to the waterreservoir27.

As the plungers 139a and a begin to move towards the left, the drivenpistons 166 and 167, which are operatively connected with the drivingpistons 139a and 140a through connecting rods 168a and 16811, are movedoutwardly. The oil in the cylinder spaces 166a and l167t1 is deliveredthrough lines 163, 143, 53 into the press cylinder 4a of the press 1.The check valve 54 prevents the oil from cylinders 166a and 167a fromflowing back into the cylinder chamber 152 of low-pressure transformer115. As the press piston 4 of the press 1 moves toward its maximum outerposition, the pressure in lines 143 and 126 increases rapidly asindicated in the pressure diagram, Figure 2. When the water pressure inthe cylinder chamber 132, which acts on the piston 134, risessufficiently toovercome the spring pressure 136, the control plunger135, in moving upwardly establishes communication between thehigh-pressure line 143 and the oil reservoir 64 through cylinder chamber123 and line 145.

-As the driving plunger assembly 139a, =1-40a of the high pressuretransformer has reached the center position b (Figure l), the drivenpistons 166 and 167 reverse their outward motion and commence to movetoward their inner dead center whereby they will draw ofi oil from thepress cylinder 4a of the press 1 through lines 53 and e 143. As aresult, the press piston 4 moves downwardly and the pressure on theworkpiece is thereby released.

' In order to further retract the press piston 4 to its initial startingposition, the valves 102, 119, 142, which are operatively connected witheach other by connecting rod 143, are turned 90 either manually ormechanically by a moving part of the high-pressure transformer by whichaction the operating control valve 102 is closed and the valves 1 19 and142 are opened. Communication between the automatic reverse valve104 andthe high-pressure accumulator 5 is thereby disrupted. On the other hand,the press cylinder 4a is connected with the cylinder chamber 152 of thelow pressure transformer 115 by by-passing the check valve 54" throughlines 124 and control valve 142. Due to the rotation of the controlvalve 119 into anopen position, the water in the cylinder space 114- cannow-escape to thewater'reservoir 27 by way of lines 113, 118 and 121 bythe action of the spring 116. As the piston 153a moves downwardly; thepiston 13% also moves downwardly and draws oil from the press cylinder40 through line 53, 124, valve 142 into the cylinder space 152 wherebythe press piston or ram 4 is returned to its starting position.

As the pressure in the cylinder space 114 drops, the pressure in thecylinder space 106 of the automatic reverse valve 104 is also loweredand the spring 107 moves the piston assembly 105-, 109, 110' to the leftand the line 103 from the control valve 102 is again connected to thecylinder chamber 114 of the low-pressure transformer. By this lastaction, the Working cycle is completed.

In preparation of the next Working cycle, the four-way valve 127 isrotated by- 90 whereby the connections to the cylinder chambers 139 and140 of the high-pressure transformer 141 are interchanged so that thepiston assembly 139a, 140a moves from the left to right if pressurefluid from the accumulator 5 is received. In order to initiate the nextworking cycle, the control valves 102, 11 9; 142 are turned into theoriginal position, as shown in Figure 3, through rod 143 whereby the newworking cycle commences.

The structure shown in Figure 4 represents a lowpressure transformermodified from that shown in Figure 3 in that a spring 216 is arrangedwithin the cylinder space 252 for forcing the piston assembly downwardlywhen the pressure in the cylinder-space 214 is reduced.

Figure 5 is an enlarged view of the high-pressure transformer indicatingthe connectinglines thereto by numerals as they appear in Figures 1 and3.

Figure 6' is a modified construction of the automatic reverse valve 104shown in Figure 3.

Instead of the piston 105 in Figure 3 being rigidly con nected with thepiston "alves 199 and 110 by a connecting rod 112 the piston 205according to the embodiment of Figure 6 is resiliently connected to thepiston valve assembly 209, 210 in the following manner:

The piston 205 is in resilient engagement with a snapring 270 by Way ofa connecting rod 271 having a shoulder 272 at its end and being guidedin a bore 273 thereof. Springs 274 and 275 on each side of the shoulder272 retain the shoulder 272 in an approximately central position. ofbore 273. Two V-shaped grooves 276 and, 277 are provided on thecircumference, of the snap ring. 270 and the snap ring is held inposition by a spring loaded ball 27S engaging one of the grooves.

When the piston 205 is first actuated by the increase in presure in line120, Figure 3, to the right, Figure 6, the piston valve assembly 209,210 does not begin to move immediately to the right but first the spring275 is compressed to a point where it exerts sufficient pressure on thesnap ring to disengage the spring loaded ball 278 after which the snapring 270 together with the piston valves 209 and 210 snap to the rightand the ball 278 engages with the groove 276.

By this action communication between lines 103 and 113 is disrupted andcommunication between lines 103 and 126 is established.

As the pressure in cylinder chamber 206 decreases, the spring 207 movesthe piston 205 to the left and the auxiliary spring 274 is compressed toa point sufiicient to disengage the ball 278 from groove 276 whereafterthe snap ring 270 together with the piston valves 209 and 210 are movedto their original position as shown in Figure 6.

From the schematic illustration of Figure l and Figure 3, the pertinentadvantage of the present invention can be readily recognized whichresides therein that the forming stroke and release stroke are performedwith a highpressure transformer at the fastest possible movement 10 froma to 001 etc a without the necessity of reversing anyvalves. With suchan arrangementit is possible to perform the forming and releasing of abig press. in'one to two seconds.

While I have shown several embodiments of my invention, it is understoodthat the same is not limited thereto but is susceptible of many changesand modifications within the scope of person skilled in the art, and Iintend to cover all such changes and modifications as encompassed by theappended claims.

I claim:

- I. A hydraulically operated press particularly for forming materialsat elevated temperatures comprising a relatively stationary part andrelatively movable part, hydraulic means including pressure supply meansoperatively connected with said press for initially closing said pressduring a first stage of operation and including piston meansdisplaceable from an initial position for supplying high-pressure to thepress and thereafter toward said initial position for releasing theapplication of said highpressure to the press, a movable actuator meansconnected to the piston means and movable continuously in one directionfor displacing said piston means both from and toward said initialposition for thereupon further actuating said relatively movable partrelatively rapidly in the closing direction to form said material andfor thereafter moving said relatively movable part in the oppositedirection during a second stage of operation.

2. A hydraulically operated press particularly for forming materials atelevated'temperatures comprising a relatively stationary part and arelatively movable part, hydraulic means including first piston meansand pressure supply means operatively connected with said press forinitially closing said press during a first stage of operation,high-pressure transformer means operatively connected with said pressuresupplymeans and said press including second piston means displaceablefroman initial position for supplying high-pressure to the press andthereafter toward said initial position for releasing the application ofsaid high-pressure to the press, a movable actuator means connected tothe second piston means and movable continuously in one direction fordisplacing said second piston means both. from and toward said initialposition for further actuation of said relatively movable part at arelatively rapid rate in the closing direction to form said material andfor thereafter moving said relatively movable part in the oppositedirection during a second stage of operation.

3. A hydraulically operated press particularly for forming materials atelevated temperatures comprising a relatively stationary part and arelatively movable part, bydraulic means. including pressure supplymeans, lowpressure transformer means including first piston meansoperatively connected with said supply means and said press forinitially closing said press during the first stage of operation, andhigh-pressure transformer means operatively connected with said pressuresupply means and said press including second piston means displaoeablefrom an initial position for supplying high-pressure to the press andthereafter toward said initial position for releasing the application ofsaid high pressure to the press, a movable actuator means connected tothe second piston means and movable continuously in one direction fordisplacing said second piston means both from and toward said initialposition for further actuation of said relatively movable part at arelatively rapid rate in the closing direction to form said material andfor thereafter moving said relatively movable part in the oppositedirection during a second stage of operation.

4. The combination according to claim 2, further comprising controlmeans for automatically bringing said high-pressure transformer intooperation after completion of said first stage of operation, saidcontrol means being responsive to the rise in pressure in said press atthe end of said initial closing operation.

5. The combination according to claim 3, further comprising controlmeans for automatically bringing said high-pressure transformer intooperation after completion of said first stage of operation, saidcontrol means being responsive to the prevailing pressure in saidlowpressure transformer at the end of said initial closing operation.

6. The combination according to claim 3, wherein control valves areincluded in said pressure transmitter.

7. The combination according toclaim 3, wherein said low-pressuretransformer includes a high-pressure piston having a relatively smalldiameter and a low-pressure piston of a relatively large size, the ratioof said diameters being such that the pressure produced by saidlowpressure piston is capable of moving said relatively movable partduring said initial closing of said press. a

8. The combination according to claim 2, wherein said high-pressuretransformer includes at least one driving actuator piston and at leastone driven piston, pressure transformation being accomplished bytransmission of power from said driving piston to said driven piston.

9. The combination according to claim 8, wherein said driving actuatorpiston is directly connected with said driven piston by means of aconnecting rod, the movement of one of said pistons being at an angle tothe movement of the other of said pistons.

;Ihe combination according to claim 2, wherein the pressure produced insaid high-pressure transformer for said further actuation of saidrelatively movable part increases progressively during said actuatingmovement.

11. The combination according to claim 2, wherein the pressure producedin said high-pressure transformer isof variable magnitude. 7

12. The combination according to claim 2, wherein the pressure in saidhigh-pressure transformer is selec tively limited in magnitude by apressure-limit valve.

13. The combination according to claim 8, wherein said driven piston ismovably guided in a cylinder including a pressure-limit valve.

14. The combination according to claim 2, wherein said high-pressuretransformer includes two driving pistons slidably arranged in coaxialcylinders and connected with each other by a rigid piston rod, twodriven pistons the movement of which is in a perpendicular direction ofthat for said driving pistons, connecting rods pivotally connecting saiddriving and said driven pistons with each other, said connecting rodsbeing disposed sub: stantially perpendicular to the direction ofmovement of said driving pistons.

15. The combination according to claim 3, wherein the working fluid from.said pressure supply means to said transmitters is. water while theworking fluid between said transmitters and said press is oil.

16. The combination according to claim 2, wherein the connection of saidsecond piston means to said actuator means comprises a linkage providingan increased mechanical advantage in transmitting the forces from saidactuator means to said piston means during movement of said actuatormeans near the position thereof corresponding to the position of thepress being fully closed.

17. A hydraulically operated press particularly an extrusion press ordrop-forge press for forming materials comprising a relativelystationary part and a relatively moveable part, hydraulic meansincluding pressure supply means, a high-pressure transformer meansoperatively connected with said pressure supply means and said pressincluding at least one driving piston and at least one driven piston,said driving piston being directly connected with sm'd driven piston bymeans of a connecting rod, the movement of one of said pistons being atan angle to the movement of the other of said pistons, pressuretransmission being accomplished by transmission of power from saiddriving piston to said driven piston for actuation of said relativelymoveable part at a relatively rapid rate in the closing direction toform said material and for thereafter moving said relatively moveablepart in the opposite direction.

18. A hydraulically operated press particularly an extrusion press ordrop-forge press for forming materials comprising a relativelystationary part and a relatively moveable part, hydraulic meansincluding pressure supply means, low-pressure transformer meansoperatively con-' -mission 'being accomplished by transmission of powerfrom said driving piston to said driven piston for further actuation ofsaid relatively moveable part at a relatively rapid rate in the closingdirection to form said material and for thereafter moving saidrelatively moveable part in the opposite direction during a second stageof operation.

References Cited in the file of this patent UNITED STATES PATENTS1,888,990 Kurath Nov. 29, 1932 2,200,998 Schnuck May 14, 1940 2,239,339Oeckl Apr. 22, 1941 2,403,912 Doll July 16, 1946 2,573,993 Sedgwick Nov.6, 1951 2,737,138 Derbyshire Mar. 6, 1956

